314 DOCS. 322, 323 APRIL 1917 My burning desire to see you and my other colleagues and mindmates more often will assure my coming back to Holland soon.[3] This summer I must first go to Switzerland, though, to be together with my children, perhaps also to spend time at a health resort in Tarasp.[4] However, my next trip will certainly take me to all of you. I am pleased that Planck and Waldeyer have written you.[5] The latter still hails from the good old pre-Treitschke days.[6] Planck did not tell me that he had written you at all; that is why I feared he had neglected to do so. The younger ones are considerably worse than they, however. I am convinced that a kind of mental epidemic is involved. For otherwise I cannot grasp why people who are thoroughly decent in their personal attitudes take on such an entirely different view with respect to public affairs. I can only draw comparison with the times of martyrdom, crusades, and witchcraft trials. Only very uncommon independent characters can escape the pressure of prevailing opinion. There seems to be no such person at the Academy.[7] Your joint paper with Droste is very interesting.[8] It is splendid that in L only first derivatives occur according to time. This is analogous to Hamilton’s function of the gravitational field. It is a pity that the deviations from Newton are so small; but ultimately, we ought to be glad that Mercury’s case has presented itself, at least.[9] My last paper will not appeal to you.[10] It is convincing only if the relativity of inertia is considered a requirement, that is, if one is convinced that inertia can be attributed entirely to an interaction with the observed mass.[11] Healthwise I am feeling considerably better again, thanks especially to the meticulous diet which my relatives here have been able to provide with the help of their southern German connections.[12] Without this help I would scarcely be able to stay here; I do not know either whether it can continue on like this.[13] Affectionate greetings also to your wife and the two de Haases, yours, A. Einstein. 323. To Felix Klein [Berlin,] 4 April 1917 Highly esteemed Colleague, Thank you very much for your kind and interesting letter. I shall not fail to read your mentioned papers in the original.[1] That which you call agnostic in your position is present also in mine, specifically, in the following form: No matter how we draw a complex from nature for simplicity’s sake, its theoretical